Impact of protein gel porosity on the digestion of lipid emulsions

The present study sought to understand how the structure of protein gels impacts lipolysis of gelled emulsions. The selected system consisted of an o/w emulsion embedded within gelatine gels. The gelatine gelled emulsions consisted of a discontinuous network of aggregated emulsion droplets, dispersed within a continuous network of gelatine. The viscoelastic properties of the gelled emulsions were dominated by the rheological behaviour of the gelatine, suggesting a gelatine continuous structure rather than a bi-continuous gel. A direct relationship between the speed of fat digestion and gel average mesh size was found, indicating that the digestion of fat within gelatine gelled emulsions is controlled by the ability of the gels microstructure to slow lipase diffusion to the interface of fat droplets. Digestion of fat was facilitated by gradual breakdown of the gelatine network, which mainly occurred via surface erosion catalysed by proteases. Overall this work has demonstrated that the lipolysis kinetics of gelled emulsions is driven by the microstructure of protein gels, this knowledge is key for the future development of structures to control fat digestion and or the delivery of nutrients to different parts of the gastrointestinal tract.